Email Service Provider
An email service provider (ESP) is the software you use to send, manage, and measure email to your users, customers, or subscribers.
An email service provider (ESP) is the software that sends email on your behalf and manages the contacts, templates, automation and reporting around it. The term covers tools for marketing campaigns, for transactional email triggered by an application, or for both.
What an ESP does
An ESP runs the sending infrastructure, handles bounces and unsubscribes, stores your contact list, provides an editor and templates, runs automations, and reports on delivery, opens and clicks for each campaign. Developers usually reach it through an email API. Marketers use the web app.
Loops is an email service provider built for software teams, covering marketing email and transactional email.
Common mistakes
Choosing on editor polish alone. The questions that matter more are whether the tool supports your sending model (campaigns, event-triggered mail, or both from one contact record), how it handles bounces and suppression, and whether your engineers can wire it in without running a second system.